1. Field of the Invention
The present invention relates to apparatus and methods for the removal of heat from electronic devices. In particular, the present invention relates to a heat sink for the removal of heat from an active surface of a wirebonded microelectronic die.
2. State of the Art
Microelectronic dice are typically housed in a protective covering referred to as a package or packaging. In one such package 200, as shown in FIGS. 6 and 7, a microelectronic die 202 is positioned in a recess 204 of a substrate 206. The microelectronic die 202 contains integrated circuitry formed therein (not shown). A back surface 208 of the microelectronic die 202 is preferably attached in the substrate recess 204 by a first layer of adhesive 212. A plurality of bond pads 214 is disposed on an active surface 216 of the microelectronic die 202, as shown in FIG. 7. The bond pads 214 are generally placed near the edges of the microelectronic die active surface 216 and are electrically connected by bond wires 218 to corresponding conductive fingers or traces 222 on the substrate 206.
Generally, portions of the conductive traces 222 are disposed on multiple tiers in the substrate recess 204 (shown as first tier 224 and second tier 226) for more effective attachment of the bond wires 218. The substrate 206 usually comprises a layer or multiple layers of dielectric material with the conductive traces 222 extending therethrough and/or therebetween (not shown), wherein the conductive traces 222 are in contact with external electrically connection devices, such as solder ball or pins (not shown), which may connect the package 200 to external electrical devices.
A lid 228 covers the recess 204 and may be attached to a first surface 232 of the substrate by a second layer of adhesive 234. The lid 228 prevents environmental contamination of the microelectronic die 202, the bond pads 214, the bond wires 218, and/or the conductive traces 222, which may lead to the damage or destruction thereof.
In another embodiment as shown in FIG. 8, an encapsulant material 236 may be disposed in the substrate recess 204 to prevent environmental contamination, rather than the attachment of a lid 228, as shown in FIG. 6.
Of course, higher performance, lower cost, increased miniaturization, and greater packaging density of integrated circuits are ongoing goals of the computer industry. As these goals are achieved, microelectronic dice 202 become smaller. Accordingly, the density of power consumption of the integrated circuit components in the microelectronic die 202 has increased, which, in turn, increases the average junction temperature of the microelectronic die 202. If the temperature of the microelectronic die 202 becomes too high, the integrated circuits of the microelectronic die 202 may be damaged or destroyed. Generally, with surface mounted microelectronic dice, such as flip-chips and quad flat packs, heat is dissipated from the back surface thereof with the attachment of heat slugs, heat pipes, heat spreaders, and the like. With wirebonded microelectronic die packages described above, heat also can be drawn out of a back surface 238 of the package 200 through the substrate 206 with the attachment of a heat dissipation device. However, the substrate 206 is general made of an organic laminate, which is a poor thermal conductor. Thus, in some cases, the substrate 206 may be made of a thermally conductive ceramic or may have an integrated heat dissipation device 242 to draw heat out of the microelectronic die back surface 208, as shown in FIG. 9.
However, as thermal management issues continue to arise, it would be advantageous to develop apparatus and techniques to effectively remove additional heat from a wirebonded microelectronic dice while requiring minimal changes to the current wirebond package process.